The present invention relates to motion control systems and, more particularly, to interface software that facilitates the creation of hardware independent motion control software.
The purpose of a motion control device is to move an object in a desired manner. The basic components of a motion control device are a controller and a mechanical system. The mechanical system translates signals generated by the controller into movement of an object.
While the mechanical system commonly comprises a drive and an electrical motor, a number of other systems, such as hydraulic or vibrational systems, can be used to cause movement of an object based on a control signal. Additionally, it is possible for a motion control device to comprise a plurality of drives and motors to allow multi-axis control of the movement of the object.
The present invention is of particular importance in the context of a mechanical system including at least one drive and electrical motor having a rotating shaft connected in some way to the object to be moved, and that application will be described in detail herein. But the principles of the present invention are generally applicable to any mechanical system that generates movement based on a control signal. The scope of the present invention should thus be determined based on the claims appended hereto and not the following detailed description.
In a mechanical system comprising a controller, a drive, and an electrical motor, the motor is physically connected to the object to be moved such that rotation of the motor shaft is translated into movement of the object. The drive is an electronic power amplifier adapted to provide power to a motor to rotate the motor shaft in a controlled manner. Based on control commands, the controller controls the drive in a predictable manner such that the object is moved in the desired manner.
These basic components are normally placed into a larger system to accomplish a specific task. For example, one controller may operate in conjunction with several drives and motors in a multi-axis system for moving a tool along a predetermined path relative to a workpiece.
Additionally, the basic components described above are often used in conjunction with a host computer or programmable logic controller (PLC). The host computer or PLC allows the use of a high-level programming language to generate control commands that are passed to the controller. Software running on the host computer is thus designed to simplify the task of programming the controller.
Companies that manufacture motion control devices are, traditionally, hardware oriented companies that manufacture software dedicated to the hardware that they manufacture. These software products may be referred to as low level programs. Low level programs usually work directly with the motion control command language specific to a given motion control device. While such low level programs offer the programmer substantially complete control over the hardware, these programs are highly hardware dependent.
In contrast to low-level programs, high-level software programs, referred to sometimes as factory automation applications, allow a factory system designer to develop application programs that combine large numbers of input/output (I/O) devices, including motion control devices, into a complex system used to automate a factory floor environment. These factory automation applications allow any number of I/O devices to be used in a given system, as long as these devices are supported by the high-level program. Custom applications, developed by other software developers, cannot be developed to take advantage of the simple motion control functionality offered by the factory automation program.
Additionally, these programs do not allow the programmer a great degree of control over the each motion control device in the system. Each program developed with a factory automation application must run within the context of that application.
Each brand or model of motion control device contains communication software that defines a communication protocol that is responsible for transmitting control codes and receiving response codes used to control the hardware to perform motion operations and to retrieve codes describing the results of the operation. This internal communication software is machine specific, and an application program written to communicate using the communication protocol associated with one brand or model of motion control device will likely not be able to communicate with the communication protocol associated another brand or model of motion control device.
Accordingly, it would be desirable for a programmer to be able to write an application program that is independent of the hardware communication protocol so that the application program may be used with different hardware devices without modification by the programmer.
In the following discussions, a number of documents are cited that are publicly available as of the filing date of the present invention. With many of these documents, the Applicant is not aware of exact publishing dates. The citation of these documents should thus not be considered an admission that they are prior art; the Applicant will take the steps necessary to establish whether these documents are prior art if necessary.
As mentioned above, a number of software programs currently exist for programming individual motion control devices or for aiding in the development of systems containing a number of motion control devices.
The following is a list of documents disclosing presently commercially available high-level software programs: (a) Software Products For Industrial Automation, iconics 1993; (b) The complete, computer-based automation tool (IGSS), Seven Technologies A/S; (c) OpenBatch Product Brief, PID, Inc.; (d) FIX Product Brochure, Intellution (1994); (e) Paragon TNT Product Brochure, Intec Controls Corp.; (f) WEB 3.0 Product Brochure, Trihedral Engineering Ltd. (1994); and (g) AIMAX-WIN Product Brochure, TA Engineering Co., Inc. The following documents disclose simulation software: (a) ExperTune PID Tuning Software, Gerry Engineering Software; and (b) XANALOG Model NL-SIM Product Brochure, XANALOG.
The following list identifies documents related to low-level programs: (a) Compumotor Digiplan 1993-14 94 catalog, pages 10-11; (b) Aerotech Motion Control Product Guide, pages 233-34; (c) PMAC Product Catalog, page 43; (d) PC/DSP-Series Motion Controller C Programming Guide, pages 1-3; (e) Oregon Micro Systems Product Guide, page 17; (f) Precision Microcontrol Product Guide.
The Applicants are also aware of a software model referred to as WOSA that has been defined by Microsoft for use in the Windows programming environment. The WOSA model is discussed in the book Inside Windows 95, on pages 348-351. WOSA is also discussed in the paper entitled WOSA Backgrounder: Delivering Enterprise Services to the Windows-based Desktop. The WOSA model isolates application programmers from the complexities of programming to different service providers by providing an API layer that is independent of an underlying hardware or service and an SPI layer that is hardware independent but service dependent. The WOSA model has no relation to motion control devices.
The Applicants are also aware of the common programming practice in which drivers are provided for hardware such as printers or the like; an application program such as a word processor allows a user to select a driver associated with a given printer to allow the application program to print on that given printer.
While this approach does isolates the application programmer from the complexities of programming to each hardware configuration in existence, this approach does not provide the application programmer with the ability to control the hardware in base incremental steps. In the printer example, an application programmer will not be able to control each stepper motor in the printer using the provided printer driver; instead, the printer driver will control a number of stepper motors in the printer in a predetermined sequence as necessary to implement a group of high level commands.
The software driver model currently used for printers and the like is thus not applicable to the development of a sequence of control commands for motion control devices.
From the foregoing, it should be clear that one primary object of the invention is to provide improved methods and devices for moving objects.
Another more specific object of the present invention is to obtain methods and apparatus for designing and deploying motion control devices in which these methods and apparatus exhibit a favorable mix of the following characteristics:
(a) allow motion control drivers to communicate with hardware in a hardware independent manner; and
(b) allow motion control streams, used by motion control drivers, to communicate with hardware in a hardware independent manner.
The present invention is, in one form, a method of and apparatus for communicating with a motion control device for moving an object. The method and apparatus of the present invention employ a special protocol to facilitate communication with the underlying motion control hardware in a manner that is independent of the specific communication protocols defined by supported motion control hardware devices. In particular, the present invention uses a communication map that maps a generic grid of mapping information cells to the actual information cells implemented by the particular hardware. Since each actual information cell may be located in different areas in memory and may transfer different values on each hardware platform, the mapping information cells translate common functions across a plurality of supported hardware implementations.